(1) Field of the Invention
The present invention relates to a license management system and others that distribute license information which makes it possible to use a content under a certain usage rule from a management device to a terminal device used by a user who requests a use of the content via a communication network and a relay device.
(2) Description of the Prior Art
In recent years, systems that distribute some digital productions, such as music, videos and games, via the Internet or digital broadcasting have been developed, and a part of them is now in a phase for practical use. For distributing these contents, the methodology of rights, management and usage control (DRM: Digital Rights Management), which restricts the number of times of reproduction (playback), moving and copying for the distributed content, has also been examined from a viewpoint of copyright protection, etc.
The conventional license management systems, as seen in the Japanese Laid-Open Patent Application Nos. 2000-48076 and 2000-293439, have been modeled to distribute license information of the content for each user together with the content itself to a recipient side to have everything managed by a user terminal side.
For example, if a user wants to purchase a right to see a content (a movie, for example) three times, the user terminal receives the content together with its license information indicating “the movie can be viewed three times” via communication from a distribution server, and the playback of the content is under the management according to the usage rule included in the license information. Once the above-mentioned license information is sent to the user terminal, the distribution server is no longer involved with the license information of the user.
The user terminal manages all the license information of the user under these systems, so that the functions of the user terminal expand which, in turn, causes complicated rights processing. As a result, there is a problem that an expensive CPU and others need to be used, and thereby the user terminal becomes expensive accordingly. There is another problem that when the hard disk of the user terminal which stores license information crashes, all the purchased license information is lost.
In order to solve these problems, a system for protecting the copyright of a content has been proposed in which a management device plays a central role in dynamically managing a usage right (license) per content which is given to a user who purchases the content and distributing license information including usage rules for the use of the content in response to a request from a user terminal so as to enable the user to use the content within the scope of the usage rules included in the license information, as disclosed in the Japanese Laid-Open Patent Application No. H10-63364.
According to this system, only simple processing is needed to enable the user to use the content within the scope of the usage rules, and thereby the user terminal can be configured at a low price. Further, as the management device dynamically manages the usage right (license information) per content which is given to the user who purchases the content, the user terminal can acquire the unrequested license information.
In the system having these advantages, terminal devices having a variety of copyright protection functions for the contents have increasingly emerged day by day, in response to the increase of the distributed contents and the request for more sophisticated copyright protection of those contents.
Some terminal devices having a copyright protection function are not directly connected to a network. A storage medium like an SD card, a printer and so on, correspond to the terminal devices of that type. The license information needs to be relayed in order for those terminal devices to acquire the license information. In this case, it is conceivable to connect the storage medium or the printer to a terminal device which is connected to the network and have that terminal device which is connected to the network relay the license information. Note that a terminal device which is connected to a network and relays license information will be referred to as a relay device hereinafter.
The relay device interprets the license information from a viewpoint of copyright protection in the process of relaying the license information from the management device to the storage medium or the printer. As a result, the relay device needs to convert the usage rules included in the license information into the usage rules dependent upon the functions of the storage medium or the printer. Therefore, when the capability of the relay device for processing the license information is lower than that of the storage medium or the printer, there may occur a problem that the license information which is supposed to be used in the terminal device cannot be acquired or the usage rules of the license information are restrained because they are restrained in the relay device. This problem occurs frequently when the version of the relay device is older than that of the terminal device.
Specifically, this problem occurs frequently when the relay device can perform the processing of the minimum unit of usage rule among the usage rules included in the license information, that is, only one playback right, while the terminal device can perform more sophisticated processing of a plural-time playback right than the relay device. In this case, the relay device must, for example, receive distribution of the one-time playback right one by one from the management device, store a plurality of one-time playback rights in itself, and distribute these one-time playback rights one by one to the terminal device after the storage is completed. This kind of processing causes inefficient communication.
On the other hand, when the management device sends the plural-time playback right to the relay device, it is conceived that the relay device subsections the plural-time playback right into the minimum unit of the one-time playback rights, and distributes them one by one to the terminal device. However, this kind of processing also causes inefficient communication, and the terminal device cannot acquire the plural-time playback right at once.
In addition, the relay device may interpret the plural-time playback right as the one-time (the minimum-unit) playback right and nullify the remaining times of the playback right. This kind of processing results in the loss of the purchased license information.
Further, if the terminal device with more sophisticated processing capability than the relay device is developed in the copyright information processing which will be further advanced and expanded in the future, the relay device will not be able to respond to such sophisticated processing.
The object of the present invention is to provide a license management system, a license management device, a relay device and a terminal device that can prevent the license information which is issued from the management device to the terminal device via the relay device from being affected by the relay device, even if there is a functional difference in processing capability of the license information between the relay device and the terminal device.